This invention relates to a conductive structure in the form of a sheet, film, tray, board, cabinet, etc., and particularly to a conductive structure maintaining strength, transparency, and color of the substrate thereof, as well as a method of manufacturing such structure.
As a conductive sheet used for packing the IC, a molded plastic sheet made of a thermoplastic resin as polyvinyl chloride blended with carbon black has been known. However, this sheet is attended by various problems that: conductivity as high as expected can not be obtained unless particles of carbon black are thickly dispersed without interruption throughout the sheet; mechanical properties intrinsic to the plastic material thereof are impaired by blending of a large quantity of carbon black; thickness of the sheet or film is limited by pin holes which may possibly be generated when the sheet or film is intended to be thinner in the course of manufacture, and thickening of the sheet leads to high cost which invites economic disadvantage; the sheet cannot be colored in other hues than black; handling of carbon black is unpreferable in view of environmental operation conditions; and conductivity of the sheet produced is considerably reduced when subjected to the secondary process as vacuum molding.
Another kind of conductive sheet made in resin blended with surfactant and dependent on melt-molding has been known, which is advantageous because of capability of maintaining transparency and color, however, followed by many disadvantages such as gradual transfer of surfactant to the sheet surface resulting in a decline of conductivity within a lapse of about a half or a full year after produced, possibility of contaminating the contents covered or wrapped by the sheet due to cozing of surfactant transferred to the surface side of the sheet, rapid lowering of static-eliminating capacity under low humidity, and insufficient conductivity.
An object of this invention is to provide a novel and improved structure excellent in conductivity and a method of manufacture thereof.
Another object of this invention is to provide a structure endowed with conductivity without impairment of mechanical properties, transparency, and color of the substrate, as well as a method of manufacture thereof.
These and other objects of the invention will become apparent in the detailed description and examples which follow.